1248: "Sphere"
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 rhomboidal
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Re: 1248: "Sphere"
Juniorhigh geometry did not sufficiently prepare me for nightschool astronomy.
 Quicksilver
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Re: 1248: "Sphere"
I'm just a slave to the oxygen.
Re: 1248: "Sphere"
Heh
This comment brought to you by the Society of Hardware / Software Engineers Who Studied Physics Trapped on the Surface of an Oblate Spheroid
This comment brought to you by the Society of Hardware / Software Engineers Who Studied Physics Trapped on the Surface of an Oblate Spheroid
Re: 1248: "Sphere"
Nobody is trapped on the surface of a sphere. We are all free to dig into it as far as we like.

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Re: 1248: "Sphere"
Love this one.
I will have to try that line on the (somewhat elderly) receptionist at the building where I work this morning when she asks me how I'm doing. I'm half expecting a blank stare (the other choice would be "Have a nice day!") in response.
Is that mean?
I will have to try that line on the (somewhat elderly) receptionist at the building where I work this morning when she asks me how I'm doing. I'm half expecting a blank stare (the other choice would be "Have a nice day!") in response.
Is that mean?

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Re: 1248: "Sphere"
Quicksilver wrote:I'm just a slave to the oxygen.
I know, right? It's hard to believe "Oxygen Addicts Anonymous" doesn't yet exist... we could even meet overy other week, when the Aerophiles Club is not using that space...!
EDIT: I mean at least until we raise the funds to open WHOAA (World Headquarters of OAA) proper...
Last edited by Wooloomooloo on Wed Aug 07, 2013 8:17 am UTC, edited 1 time in total.
Re: 1248: "Sphere"
dalcde wrote:Surface of a sphere? A sphere is already a surface iirc.
According to the OED, it seems to depend whether you're talking geometry or mathematics. In mathematics it's the set of points equidistant from a given point; in geometry it's the solid body whose surface is a mathematical sphere. And surprisingly, the "geometrical" sense is over 500 years older:
R.Record wrote:A Sphere is a sound figure, made by the tournynge of half a circle, tyll it ende where it began to be moued
xtifr wrote:... and orthogon merely sounds undecided.
Re: 1248: "Sphere"
Am I the only one raging about the fact that the Earth is not a sphere or an oblate spheroid. Randall, please refer to this.
 Negrebskoh
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Re: 1248: "Sphere"
Was expecting comments about a spherical universe, sees comments about the shape of this tiny little planet.
The universe is too big for earthshape talk.
The universe is too big for earthshape talk.

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Re: 1248: "Sphere"
squonk wrote:Nobody is trapped on the surface of a sphere. We are all free to dig into it as far as we like.
Well, strictly speaking, we are also free to make a ladder to the moon  I'd expect you'd actually get farther with that using conventional equipment than with the digging  unless we're getting into TauTona territory here, but that's hardly typical stuff; with that level of effort, one could also just nick the keys to a Soyuz craft and make a dashing escape...
Re: 1248: "Sphere"
squonk wrote:Nobody is trapped on the surface of a sphere. We are all free to dig into it as far as we like.
I let civil engineers dig the holes, which I sometimes travel through. Some of the material they dig out is used to make bubbles on the surface of the sphere, like the one I am in now. Some of the bubbles float around the sphere with me inside. So, civil engineers make the sphere fluffy, and I live the fluffiness.
EDIT: Nuclear weapons engineers attempt to make the world less fluffy. Sphericity is not an improvement.
Re: 1248: "Sphere"
keithl wrote:EDIT: Nuclear weapons engineers attempt to make the world less fluffy. Sphericity is not an improvement.
You could use those nuclear weapons to correct the local gravitation errors (gravition direction not lining up with the vector to the centre of the ball and the likes). Imagine what a few hundred nuclear bombs could achieve for GPS! And you wouldn't make the sphere less fluffy by that, as a lot depends on the density of the matter inside the ball.
Re: 1248: "Sphere"
Even if she got off the sphere, she'd still be stuck inside a cone.

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Re: 1248: "Sphere"
Darn it, xkcd should carry some sort of warning (yeah okay it sort of does  I swear I'm not a liberal arts major!) about potential deleterious side effects to one's IQ  I distinctly feel a whole lot dumber after somehow ending up on the wikipedia page about Lagrange points and utterly failing to grasp why L4 and L5 are considered stable in spite of them being high points in the gravity potential chart of the area (the TL;DR answer is "because we say so; also, Coriolis  you know, that thing you might have heard mentioned in school but never understood and never applied it anywhere ever again; also, they're not stable in the sense you expect  the disturbed object doesn't actually tend to return to the exact L point")...
Re: 1248: "Sphere"
Though technically it would be an oblate spheroid. Unless she is trapped on some smallerthanEarth sphere, which was the fault, somehow, of her astronomy class.
I must admit that if I read that in a course syllabus, I'd be intrigued
I must admit that if I read that in a course syllabus, I'd be intrigued

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Re: 1248: "Sphere"
funny! latest comic from savage chickens is on smalltalk too
Re: 1248: "Sphere"
orthogon wrote:dalcde wrote:Surface of a sphere? A sphere is already a surface iirc.
According to the OED, it seems to depend whether you're talking geometry or mathematics. In mathematics it's the set of points equidistant from a given point; in geometry it's the solid body whose surface is a mathematical sphere. And surprisingly, the "geometrical" sense is over 500 years older:R.Record wrote:A Sphere is a sound figure, made by the tournynge of half a circle, tyll it ende where it began to be moued
Wait... geometry is not a subset of mathematics? When the chirp did that happen?
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"The Planck length is 3.81779e33 picas."  keithl
" Earth weighs almost exactly π milliJupiters"  whatif #146, note 7
Re: 1248: "Sphere"
Trapped in a pillar of decaying flesh.
"The Machine Stops", by E. M. Forster (1909)
Barry Schwartz TED Talk: "The Paradox of Choice" (Featuring the True Secret to Happiness)
Barry Schwartz TED Talk: "The Paradox of Choice" (Featuring the True Secret to Happiness)
Re: 1248: "Sphere"
cellocgw wrote:orthogon wrote:dalcde wrote:Surface of a sphere? A sphere is already a surface iirc.
According to the OED, it seems to depend whether you're talking geometry or mathematics. In mathematics it's the set of points equidistant from a given point; in geometry it's the solid body whose surface is a mathematical sphere. And surprisingly, the "geometrical" sense is over 500 years older:R.Record wrote:A Sphere is a sound figure, made by the tournynge of half a circle, tyll it ende where it began to be moued
Wait... geometry is not a subset of mathematics? When the chirp did that happen?
You see the words "in general" just after "mathematics"? Oh, it is there, right between the lines.
Re: 1248: "Sphere"
Klear wrote:cellocgw wrote:orthogon wrote:dalcde wrote:Surface of a sphere? A sphere is already a surface iirc.
According to the OED, it seems to depend whether you're talking geometry or mathematics. In mathematics it's the set of points equidistant from a given point; in geometry it's the solid body whose surface is a mathematical sphere. And surprisingly, the "geometrical" sense is over 500 years older:R.Record wrote:A Sphere is a sound figure, made by the tournynge of half a circle, tyll it ende where it began to be moued
Wait... geometry is not a subset of mathematics? When the chirp did that happen?
You see the words "in general" just after "mathematics"? Oh, it is there, right between the lines.
I was merely quoting the OED, which has separate entries for "sphere" for the fields of "mathematics" and "geometry". However, the OED's own entry for "geometry" begins "the branch of mathematics...", which is kind of inconsistent.
On the other hand, wiktionary also has separate entries for "mathematics" and "geometry", but the definitions are reversed with respect to those in the OED.
xtifr wrote:... and orthogon merely sounds undecided.
Re: 1248: "Sphere"
keithl wrote:squonk wrote:Nobody is trapped on the surface of a sphere. We are all free to dig into it as far as we like.
I let civil engineers dig the holes, which I sometimes travel through. Some of the material they dig out is used to make bubbles on the surface of the sphere, like the one I am in now. Some of the bubbles float around the sphere with me inside. So, civil engineers make the sphere fluffy, and I live the fluffiness.
EDIT: Nuclear weapons engineers attempt to make the world less fluffy. Sphericity is not an improvement.
Given that the subject is astronomy, I don't think we're talking about the 2 dimensional surface of the 3sphere we call Earth, I think it's the 3d surface of the 4sphere we call the universe. I defy you to drill into that.
The story of my life in xkcdmafia:
Tigerlion wrote:Well, I imagine as the game progresses, various people will be getting moody.
BoomFrog wrote:I still have no idea what town moody really looks like.
 mathmannix
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Re: 1248: "Sphere"
orthogon wrote:I was merely quoting the OED, which has separate entries for "sphere" for the fields of "mathematics" and "geometry". However, the OED's own entry for "geometry" begins "the branch of mathematics...", which is kind of inconsistent.
On the other hand, wiktionary also has separate entries for "mathematics" and "geometry", but the definitions are reversed with respect to those in the OED.
Hmmm... if only there were some way to reconcile the two sources. If only we could determine which one was the more authoritative, then perhaps we could somehow change the other. </sarcasm>
I hear velociraptor tastes like chicken.
Re: 1248: "Sphere"
moody7277 wrote:Given that the subject is astronomy, I don't think we're talking about the 2 dimensional surface of the 3sphere we call Earth, I think it's the 3d surface of the 4sphere we call the universe. I defy you to drill into that.
Heresy! We all know the universe (to be exact, this universe) has at least 11 dimensions, or whatever the String Theorists are up to these days. //Runs off to ask the Higgs Boson its opinion of string theoreticians.
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"The Planck length is 3.81779e33 picas."  keithl
" Earth weighs almost exactly π milliJupiters"  whatif #146, note 7
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"The Planck length is 3.81779e33 picas."  keithl
" Earth weighs almost exactly π milliJupiters"  whatif #146, note 7
 San Fran Sam
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Re: 1248: "Sphere"
Now if the earth was a geode, that would be cool.
Re: 1248: "Sphere"
Demki wrote:Am I the only one raging about the fact that the Earth is not a sphere or an oblate spheroid. Randall, please refer to this.
Deep breath everyone. Randall didn't say it's a sphere. His fictional character who recently took an entrylevel astronomy course called it a sphere.
Adam
Re: 1248: "Sphere"
Isn't saying that Earth isn't a sphere a little silly? I mean, if you shrunk it to the size of a football, it would look just like a perfect sphere. I wager you'd have to do some quite precise measurements to find out it's not a sphere. And hey, guess what? Perfect spheres don't exist. Earth isn't a perfect sphere, but it's close enough.
 mathmannix
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Re: 1248: "Sphere"
Klear wrote:Isn't saying that Earth isn't a sphere a little silly? I mean, if you shrunk it to the size of a football, it would look just like a perfect sphere. I wager you'd have to do some quite precise measurements to find out it's not a sphere. And hey, guess what? Perfect spheres don't exist. Earth isn't a perfect sphere, but it's close enough.
More or less agree... we should distinguish between the two mathematical (/geometrical/physics) definitions of sphere and the realworld "goodenough" spheres. Sure, a baseball, basketball, bowling ball, etc. * are "goodenough" spheres, as are the sun, planets, and the larger moons in the solar system. I am happy calling Earth a sphere under this definition.
*  but not a football (at least the American kind)
EDIT: I don't know much about small things, but are there perfect spheres in nature? Either macroscopic (down to molecular level anyway) like a soap bubble, or microscopic like a proton?
I hear velociraptor tastes like chicken.
 davidstarlingm
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Re: 1248: "Sphere"
mathmannix wrote:Klear wrote:Isn't saying that Earth isn't a sphere a little silly? I mean, if you shrunk it to the size of a football, it would look just like a perfect sphere. I wager you'd have to do some quite precise measurements to find out it's not a sphere. And hey, guess what? Perfect spheres don't exist. Earth isn't a perfect sphere, but it's close enough.
More or less agree... we should distinguish between the two mathematical (/geometrical/physics) definitions of sphere and the realworld "goodenough" spheres. Sure, a baseball, basketball, bowling ball, etc. * are "goodenough" spheres, as are the sun, planets, and the larger moons in the solar system. I am happy calling Earth a sphere under this definition.
Come now. 0.3% is a startling deviation! At bowlingball size, we're talking about more than half a millimetre (6.768 whole micrometres, to be exact) of variation!
I don't know much about small things, but are there perfect spheres in nature? Either macroscopic (down to molecular level anyway) like a soap bubble, or microscopic like a proton?
A soap bubble certainly isn't, as it will be deformed by air resistance opposed to its initial velocity, gravitational pull, and chaotic periodic undulations between the two. A proton is really a wave, so that's not particularly spherical either. Its field is spherical at rest, but its ground state is always high enough that it won't be at rest, so that's out. Same thing with electrons, although they're typically closer. The sun is actually more spherical than the Earth.
I suppose a superheavy nonrotating black hole's Schwartzchild radius is a pretty good sphere.
Re: 1248: "Sphere"
Astronomer Fritz Zwicky referred to his colleagues at Mount Wilson Observatory as spherical bastards, because "they are bastards from all directions". He is now in Pedant's Hell for all eternity, reciting the coefficients for the exact spherical harmonic description of the earth. With every landslide and earthquake, he must start over. Perhaps some pedants here would like to join him.
I use the sphere for most orbitrelated calculations, the first order J_{2} geoid for a few. Montenbruck (2011) comes with a CD that includes a table of the high order spherical coefficients of the geoid, accurate enough to calculate the orbits of the LAGEOS Laser Geodesy satellites to fractions of millimeter (with corrections for relativistic frame drag). We can measure the continental drift of ground laser stations in real time. In a pedant pissing contest, the LAGEOS team wins.
I use the sphere for most orbitrelated calculations, the first order J_{2} geoid for a few. Montenbruck (2011) comes with a CD that includes a table of the high order spherical coefficients of the geoid, accurate enough to calculate the orbits of the LAGEOS Laser Geodesy satellites to fractions of millimeter (with corrections for relativistic frame drag). We can measure the continental drift of ground laser stations in real time. In a pedant pissing contest, the LAGEOS team wins.
Re: 1248: "Sphere"
keithl wrote:Astronomer Fritz Zwicky referred to his colleagues at Mount Wilson Observatory as spherical bastards, ...
Bob Dylan advised us to 'gather round people'. Maybe that's who he was talking about.
Re: 1248: "Sphere"
Wooloomooloo wrote:Darn it, xkcd should carry some sort of warning (yeah okay it sort of does  I swear I'm not a liberal arts major!) about potential deleterious side effects to one's IQ  I distinctly feel a whole lot dumber after somehow ending up on the wikipedia page about Lagrange points and utterly failing to grasp why L4 and L5 are considered stable in spite of them being high points in the gravity potential chart of the area (the TL;DR answer is "because we say so; also, Coriolis  you know, that thing you might have heard mentioned in school but never understood and never applied it anywhere ever again; also, they're not stable in the sense you expect  the disturbed object doesn't actually tend to return to the exact L point")...
L4 and L5 are stable, because they're just off the peak of those high points. L4 and L5 are "rolling down hill" but the hill is rushing along after them, like a surfer.
L4 and L5 are also very volatile, small changes in velocity can send one rapidly sliding down off the stable point, requiring a lot more energy to remain there, unlike L1, L2, and L3.
 W3ird_N3rd
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Re: 1248: "Sphere"
I'm not trapped. I can leave any time I want.
The record is 12 kilometers (http://en.wikipedia.org/wiki/Kola_Superdeep_Borehole) and squishy meatbags can't survive even that little.
squonk wrote:Nobody is trapped on the surface of a sphere. We are all free to dig into it as far as we like.
The record is 12 kilometers (http://en.wikipedia.org/wiki/Kola_Superdeep_Borehole) and squishy meatbags can't survive even that little.
Re: 1248: "Sphere"
"Do you know like we were saying? About the Earth revolving? It's like when you're a kid. The first time they tell you that the world's turning and you just can't believe it because everything looks like it's standing still. I can feel it. The turn of the Earth. The ground beneath our feet spinning at a thousand miles an hour. And the entire planet is hurtling around the sun at 67 thousand miles an hour and I can feel it. We're falling through space, you and me. Clinging to the skin of this tiny little world and if we let go... That's who I am."
—The Doctor
Re: 1248: "Sphere"
davidstarlingm wrote:Come now. 0.3% is a startling deviation! At bowlingball size, we're talking about more than half a millimetre (6.768 whole micrometres, to be exact) of variation!
6.7 um > 0.5 mm ?
You may have misplaced an order of magnitude or three.
Re: 1248: "Sphere"
"How am you, Bizarro Randall?"
"Me am free on surface of giant cube!"
"Me am free on surface of giant cube!"
Re: 1248: "Sphere"
Mikeski wrote:davidstarlingm wrote:Come now. 0.3% is a startling deviation! At bowlingball size, we're talking about more than half a millimetre (6.768 whole micrometres, to be exact) of variation!
6.7 um > 0.5 mm ?
You may have misplaced an order of magnitude or three.
See, I KNEW there was something wrong about that post. I was wrong about which part though (simple arithmetic is HARD!), but hey, one day I'll be right.
Spoiler:
Re: 1248: "Sphere"
We're not just "trapped on the surface of a sphere". That's the understatement of a lifetime.
We are a thin film of life growing in the wet grooves on the surface of a rock.
Which is in turn a thin crust cooled on the surface of a ball of hot magma.
And we're blanketed from cold hard vacuum by only a thin wisp of gasses.
And all of that is a tiny mote of dust floating in the void of space.
Around a gigantic, billionsofyearsold ongoing thermonuclear fireball.
At just barely the right distance to neither burn to a crisp nor freeze solid.
And that fireball is a tiny speck in one thin wisp of a swirl of billions more like it.
And that swirl is only one grain in a tiny clump of sand in an infinite desert.
"Trapped on the surface of a sphere." Hah.
[EDIT: Typo.]
We are a thin film of life growing in the wet grooves on the surface of a rock.
Which is in turn a thin crust cooled on the surface of a ball of hot magma.
And we're blanketed from cold hard vacuum by only a thin wisp of gasses.
And all of that is a tiny mote of dust floating in the void of space.
Around a gigantic, billionsofyearsold ongoing thermonuclear fireball.
At just barely the right distance to neither burn to a crisp nor freeze solid.
And that fireball is a tiny speck in one thin wisp of a swirl of billions more like it.
And that swirl is only one grain in a tiny clump of sand in an infinite desert.
"Trapped on the surface of a sphere." Hah.
[EDIT: Typo.]
Last edited by Pfhorrest on Wed Aug 07, 2013 10:07 pm UTC, edited 1 time in total.
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 davidstarlingm
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Re: 1248: "Sphere"
Mikeski wrote:davidstarlingm wrote:Come now. 0.3% is a startling deviation! At bowlingball size, we're talking about more than half a millimetre (6.768 whole micrometres, to be exact) of variation!
6.7 um > 0.5 mm ?
You may have misplaced an order of magnitude or three.
It seems I misplaced a decimal point.
Correction: "Come now, 0.3% is a startling deviation! At bowlingball size, we're talking about more than half a millimetre (676.8 whole micrometers, to be exact) of variation!"
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